Russia is considering increasing its assistance to Iran’s nuclear programme in response to America’s calls for Nato expansion eastwards and the presence of US Navy vessels in the Black Sea delivering aid to Georgia.

The Kremlin is discussing sending teams of Russian nuclear experts to Tehran and inviting Iranian nuclear scientists to Moscow for training, according to sources close to the Russian military.

Moscow has been angered by Washington’s promise to give Georgia £564m in aid following the Russian invasion of parts of the country last month after Tbilisi’s military offensive. Kremlin officials suspect the US is planning to rearm the former Soviet republic and is furious at renewed support for attempts by Georgia and Ukraine to join Nato.

Last week a third US Navy ship entered the Black Sea with aid bound for Georgia. Moscow has accused the Americans of using the vessels to deliver weapons but has failed to provide any evidence.

Vladimir Putin, the prime minister of Russia, who has been the driving force during the crisis, has declared he will take unspecified action in response.

“Everything has changed since the war in Georgia,” said one source. “What seemed impossible before, is more than possible now when our friends become our enemies and our enemies our friends. What are American ships doing off our coast? Do you see Russian warships off the coast of America?

“Russia will respond. A number of possibilities are being considered, including hitting America there where it hurts most – Iran.”

Increasing nuclear assistance to Iran would sharply escalate tensions between Moscow and Washington. Over the past 10 years Russia has helped Iran build its first nuclear power station in Bushehr. Iran claims the plant is for civilian purposes. Officially at least, Moscow accepts that. The West has little doubt the aim is to build a nuclear bomb.

But diplomats say that despite its help with the Bushehr plant, Moscow has so far played a constructive role as a mediator between the regime in Tehran and the West and by backing United Nations sanctions.

Earlier this year, in one of his last actions as president, Putin added Russia’s stamp of approval to a UN security council resolution imposing fresh sanctions against Iran.

The document bans, with the exception of the Bushehr project, dual-technology exports that could be used for civil nuclear purposes and missile production.

“After the war in Georgia it’s difficult to imagine relations between Russia and America getting worse,” said a western diplomat. “Russia giving greater nuclear assistance to the Iranians would do the trick – that’s for sure.”

Last month Russia agreed to sell missiles to Syria. “The mood among the hawks is very bullish indeed,” said one source who did not rule out a resumption of Russian military action in Georgia to take the port of Batumi, where American vessels are delivering aid.

Hardliners were infuriated last week by the visit to Georgia of Dick Cheney, the American vice-president. “Georgia will be in our alliance,” Cheney said. He also visited Ukraine, whose Nato aspirations could make it the next flashpoint between Russia and America.

However in Kiev, the Ukrainian capital, events appeared to be moving Moscow’s way. Viktor Yushchenko, the pro-western president, is fighting to stay in power in a crisis that could see him impeached.

“I’m amused by claims in the West that Russia is the loser in this crisis,” said a former Putin aide. “What would Washington do if we were arming Cuba the way it armed Georgia? The postSoviet days when we could be pushed around are over.”